3. V. gastroepiploica (e) comes from the greater curvature of the stomach and ascending limb of the great omentum. It empties into the vena portæ ventrodextrad of the opening of the coronaria ventriculi, or sometimes in common with it.
4. V. gastrolienalis (c).—The gastrosplenic is one of the veins which unite to make up the portal vein. It is formed by three branches: one (g) from the horizontal or gastric portion of the pancreas, one (h) from the stomach and gastric end of the spleen, the third and largest (i) from the caudal end of the spleen and descending limb of the great omentum. The three branches unite and the common trunk joins the superior mesenteric vein (b) to form the portal vein as above [described].
5. V. mesenterica superior (b).—The superior mesenteric vein receives the blood from the small and large intestines. It is formed by numerous branches which follow and have the same name as the corresponding arteries. It receives also the inferior mesenteric (j) from the large intestine. The numerous branches unite, and the main trunk thus formed joins the gastrosplenic (c), and the two united become the portal vein (a).
Vena iliaca communis. Common Iliac Vein ([Fig. 126], w; [Fig. 127], [page 310]).
The common iliac veins ([Fig. 126], w) are the two large vessels which unite in the sacral region to form the inferior vena cava (a). Each is a large vessel, usually four or five centimeters in length, which is formed by the junction of the large external iliac vein with the smaller hypogastric vein (z). The left common iliac usually receives the V. sacralis media (o); other lateral branches are as a rule not received by the common iliac veins.
There is much variation as to the formation of the common iliac veins and their union to form the vena cava. On this subject the paper by McClure, in the American Naturalist, vol. XXXIV. p[p. 135]-198 (March, 1900), may be consulted with profit. The more typical variations may be classified as follows: (1) The two common iliac veins may be longer than usual, so that the vena cava is formed farther craniad than usual. (2) There may be in the abdominal region two separate veins (venæ cardinales) representing the inferior vena cava, these uniting in the region of the kidneys. (3) The vena sacralis media may enter into the left common iliac (the usual condition); or the right common iliac (as in [Fig. 126]); or it may fork, one branch passing to the left, the other to the right common iliac.
Branches of the common iliac veins:
1. V. sacralis media ([Fig. 126], o).—This follows the course of the corresponding artery and usually enters the left common iliac.
2. V. hypogastrica (or iliaca interna) (z).—The hypogastric or internal iliac vein joins the medial side of the external iliac to form the common iliac (w). Its branches follow the branches of the corresponding artery except that the vein from the bladder (umbilical vein) joins the V. hemorrhoidalis media. Also the vena glutea inferior receives a large superficial communicating branch ([Fig. 163], k′) from the vena saphena parva. This branch leaves the saphena parva ([Fig. 163], k) at the popliteal space, and passes over the lateral surface of the biceps muscle to its proximal end. Here it passes between the biceps and caudofemoralis to join the vena glutea inferior.
3. V. iliaca externa ([Fig. 127], [page 310]).—This vein follows the corresponding artery, collecting the blood from the posterior extremity. Its branches are the same and have in general the same distribution as those of the artery. The vein has, however, certain branches in addition to those of the artery, resulting in a somewhat different general arrangement of vessels; it will be necessary therefore to give an account of the system of veins from the foot and lower leg.